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Description/Abstract

The visual search task carried out by X-ray screening personnel has begun to be investigated in a number of recent experiments. The goal of the present thesis was, therefore, to extend previous examinations of the factors that may be detrimental to screener performance, to understand those factors in more detail, and to bring those factors to bear upon current models of visual search. It has been argued that screener performance is impaired by searching for infrequent targets (the prevalence effect), by searching for several targets simultaneously (the dual-target cost), and by the tumultuous environment in which screeners work . Over the course of six experiments, these factors, and, in some cases, the interaction between these factors, was examined. Experiments 1, 2 and 3 explored the role that the prevalence effect and the dual-target cost have upon the performance of untrained participants. Experiment 4 revealed that airport screeners are, in fact, vulnerable to both the prevalence effect and the dual-target cost, highlighting the relevance of the present work to those working in an applied environment. Experiment 5 tested the impact of ambient noise upon search performance and the dual-target cost, and found that ambient noise has no deleterious impact. Experiment 6 set the foundation for future research involving the impact of external distractions upon search performance, with the results showing that observers are slowed substantially when conducting even a simple mental arithmetic in conjunction with a search task. Based on the results from the experiments, it appears that actual screener performance could be improved by increasing the prevalence of ‘dummy’ items, as well as tasking with screeners to search for only a single target at any one time. Efforts could also be made to reduce sources of external distraction.